1. Technical Field
The present invention relates to a MEMS (Micro Electro Mechanical System) sensor, a method of manufacturing the MEMS sensor, an electronic apparatus, and the like.
2. Related Art
As a silicon MEMS acceleration sensor with a CMOS integrated circuit for example, a reduction in size and cost for this type of MEMS sensor is rapidly progressing. The application and market of the MEMS sensor are expanding. In a main device form, an IC chip that converts a physical quantity into an electric signal and outputs the same is made into one package by a mounting process after a wafer process in most cases. For achieving an extreme reduction in size and cost, a technique of integrally forming a sensor chip and an IC chip by a wafer process is required (refer to JP-A-2006-263902).
This type of MEMS sensor has such characteristics that sensitivity is enhanced as the mass of a movable weight portion increases. For increasing the mass of the movable weight portion, in JP-A-2006-263902, the movable weight portion is formed of an integral structure including multi-layer wiring that is formed simultaneously with a multi-layer wiring layer of an LSI (paragraph 0089 and FIG. 25).
The movable weight portion vibrates in a Z-direction that is perpendicular to a substrate. The movable weight portion is formed only of the wiring layer. Since all inter-layer insulating layers are removed, the once formed inter-layer insulating layers cannot be used as a weight.
In FIG. 39 of JP-A-2006-263902, a structure in which the periphery of a multi-layer wiring structure is covered with an insulating film is disclosed (refer to paragraph 0114). In FIG. 39 of JP-A-2006-263902, however, since a conductive layer below the movable weight portion is removed by etching, only two layers of the multi-layer wiring in the movable weight portion can be used. In addition, also an inter-layer insulating layer between the two wiring layers cannot be used as a weight.